Conventionally, high-pressure discharge lamp lighting devices used for lighting high-pressure discharge lamps have been proposed (for example, see JP 2010-135195 A (hereinafter, referred to as “Literature 1”)). In the high-pressure discharge lamp lighting device disclosed in Literature 1, a full bridge circuit converts a DC output of a step-down chopper circuit into an AC current having a rectangular wave and supplies the AC current to a lamp (high-pressure discharge lamp).
In this high-pressure discharge lamp lighting device, by applying a high-voltage pulse to a lamp using an igniter circuit at a startup time, insulation breakdown of the lamp is caused, and glow discharge occurs. Thereafter, the lamp transits to arc discharge from the glow discharge, so that light fluxes rise.
The full-bridge circuit is configured by connecting first and second arms each formed by a series circuit of two transistors in parallel with each other, a set of transistors that are diagonally located are caused to be simultaneously in the On state, and On/Off of each set is alternately switched. Here, out of the transistors configuring each arm, a high potential-side transistor is caused to be in the On state when a low potential-side transistor is in the Off state. Thus, in order to cause the high potential-side transistor to be in the On state, a bootstrap capacitor supplying electric charge to a gate electrode of the transistor is arranged.
Here, in an unloaded condition before the startup of the discharge lamp, it may be considered to perform a startup operation in a speedy manner by shortening a time required for raising the output voltage of the step-down chopper circuit up to a predetermined voltage by operating the step-down chopper circuit during the process of charging the bootstrap capacitor. However, in a case where the full bridge circuit is operated in a state in which the output voltage of the step-down chopper circuit is raised by operating the step-down chopper circuit during the process of charging the bootstrap capacitor, when the load forms a short circuit, there is a problem in that an overcurrent flows in the circuit.
In addition, in the high-pressure discharge lamp lighting device disclosed in Literature 1, in a case where the step-down chopper circuit is a non-insulation type, when the load forms a short circuit at the start-up time, energy input from the power supply side is delivered to the output side even in a case where the step-down chopper circuit is stopped, and there is a problem in that an overcurrent flows in the circuit.